I remember reading somewhere that modern seatbelts are a tradeoff in design. For the buckle to be big enough to not deform in an accident it would have to be much heavier and latch stronger and less people would use them. They had to design them light, simple and as minimally intrusive as possible so the most people would wear them. The baby/toddler carriers/seats are a good example, it takes a lot longer to buckle them in than it does an adult and if it took the adult that long most would just skip the seatbelt.